Conductive backing for printing on hollow articles



6, 1967 I D. M. FREDRICKSON 3,359,890

CONDUGTIVE BACKING FOR PRINTING ON HOLLOW ARTICLES Filed Jan. 5, 1966 SOURCE OF POTENTIAL SOURCE OF POTENTIAL SOURCE OF POTENTIAL INVENTOR IGAS I DONALD M. FREDRICKSON ATTORNEY United States Patent 3,359,890 CONDUCTIVE BACKING FOR PRINTING 0N HOLLOW ARTICLES Donald Marvin Fredrickson, Deerfield, Ill., assignor to American Can Company, New York, N.Y., a corporation of New Jersey Filed Jan. 5, 1966, Ser. No. 518,956 10 Claims. (Cl. 101-35) ABSTRACT OF THE DISCLOSURE This invention relates generally to electrostatic printing and more particularly to a process and means for electrostatic printing on external surfaces of hollow articles, such as glass bottles and the like.

The art of electrostatic printing is receiving increasing attention. Representative of the prior art is the electrostatic printing system disclosed in United States Patent 3,081,698, issued to Clyde 0. Childress and Louis J. Kabell on Mar. 19, 1963. This patent discloses a method and means for printing on sheets of paper and the like utilizing means which may include an electrically charged conductive stencil wherein the printing areas comprise a fine-mesh open screen while the non-printing areas are masked. The paper to be printed is backed by a conductive plate carrying a charge opposite to that on the stencil so that particles of material, such as finely divided printing powder, applied to the stencil, are charged thereby and are propelled through the electrostatic field between stencil and plate and thus onto the paper interposed therebetween to effect the desired printing operation.

An object of the present invention is to provide a method and means for electristatically printing on the exterior surface of a hollow article, where the interior surface is difficult or impractical to engage or contact uniformly with a conventional conductive plate.

Another object of the invention is the provision of a method and means for producing within the article an electroconductive gaseous atmosphere that uniformly contacts the interior surface of the article opposite the exterior surface to be printed upon.

Still another object of the invention is the provision of means for ionizing gas within the article to produce the gaseous electroconductive atmosphere therein.

Yet another object of the invention is the production of ionized gas externally of the article and passage of this ionized gas to and through the article during the electro' static printing operation.

Other objects and advantages of the invention will be apparent as it becomes better understood from the following description which, when read in connection with the accompanying drawings, discloses a preferred embodiment of the invention.

Referring to the drawings:

FIG. 1 is a schematic illustration of one form of the invention; and

FIG. 2 is a similar illustration of another form of the invention.

3,359,890 Patented Dec. 26, 1967 As shown in FIG. 1, a hollow article, such as a glass bottle 10, is disposed with its exterior surface spaced at relatively short distance from a printing element 11 to which printing material may be fed by an applicator 12 or in any suitable manner well known in the art. The printing element 11 is representative of any equivalent element known in the art, such as the cylinder used in the gravure method of electrostatic printing or the stencils of different shapes shown in the above mentioned United States patent to Childress et al. In electrostatic printing generally, the printing element is charged, as through a ground, with a predetermined polarity at a potential sufiicient, with relation to an opposite polarity on a backing plate or other conductive backing element, to effect the desired transfer of printing particles through the established electrostatic field onto the interposed surface to be printed upon.

Obviously such printing requires that the backing plate or other conductive backing element must substantially conform to the shape of the surface to be printed upon, and also that it be substantially parallel to that surface. This presents a problem in electrostatic printing on the exterior surfaces of hollow articles such as bottles which not only vary in shape, but also usually make difficult if not impossible, the insertion and satisfactory disposition therein of a conventional backing element.

To solve this problem, this invention provides a method and means for producing the desired charge on the hollow article by ionizing gas within the article, thus producing a gaseous conductive backing means at 15 that effectively conforms to the shape of the interior surface of the bottle 10 that is spaced by a substantially uniform thickness of glass from the exterior surface 16 to be printed upon.

Ionization of the gas, such as air, within the bottle 15,

5 is effected by an electric potential from a source 17 conducted to a pair of electrodes 18 mounted in an insulating member 19, that may be in the form of a stopper for the bottle opening. The electrodes are arranged in parallel leaving a gap between them suflicient for the applied potential to effect ionization of the air in the bottle.

It was found that a print could readily be made on a bottle with this treatment at 3000 volts over a relatively large A inch gap, with better resolution than normal and with nearly excessive ink density using a single brush pass.

The following is an example of electrostatic printing by this method: Using an ionizing potential of 15000 volts from source 17, and a resultant voltage of 2000 volts at or near contact to the glass surface 16, an excellent print was made on a glass bottle. The print had good density, with resolution such that the individual wires of the 200 line stencil screen 11 were sharply defined.

In the form of the invention shown in FIG. 2, air or other ionizable gas is forced by a pump 25 through suitable conduits 26 to an ionizer 27 and thence to and through the interior of the bottle 10 during the printing operation. The energy required by the external ionizer 27 is provided by a source of potential 28.

The ionized air fed from the ionizer 27 and through the bottle 10 decreases the amount of ionization required to be effected by the electrodes 18. This supplemental flow of ionized air increases the efiiciency of the method and means of the invention, particularly when high speed production is required.

In this second form of the invention, the potential at source 17 should be between 2000 and 15000 volts, and at source 28 the potential should be in the vicinity of 5000 to 20000 volts.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes may be made in the construction and arrangement of the parts without departing from the spirit and scope of the invention.

I claim:

1. In a process for electrostatically printing on the outer surface of a hollow article utilizing printing particles electrostatically charged at a predetermined polarity from a source of electric potential, and directed toward an area of said outer surface to be printed upon, the steps of:

establishing an electrical potential within said hollow article;

ionizing gas within the hollow article to produce a gaseous conductive element that extends over the interior surface of the article opposite said outer surface area; and

creating an electrostatic field between said inner gaseous conductive element and said charged particles thereby eifecting attraction of said particles to said outer area of the article for printing thereon.

2. In an electrostatic printing process as set forth in claim 1, the additional steps of generating ionized gas external to said article, and feeding said ionized gas to and through the hollow interior of said article during the printing operation.

3. The process as set forth in claim 2 wherein air is ionized.

4. The method set forth in claim 1 wherein the electric potential producing the ionized gas in the article is between 2000 and 15000 volts.

5. The method set forth in claim 2 wherein the electrical potential of said hollow article is between 2000 and 15000 volts and the electric potential producing the ionized gas externally of the article is about 5000 to 20000 volts.

6. In an apparatus for printing by electrostatic deposition on gas-filled hollow articles wherein an element is spaced at a substantially uniform distance from an external area of a hollow article to be printed upon, and the thickness of said article through said area is substantially uniform, the combination comprising:

a source of electric potential:

21 pair of electrodes mounted in an insulating member and extending therefrom in parallelism one relative to the other leaving a predetermined gap therebetween, said electrodes being insertable into the gasfilled interior of said article and connected to said source of electric potential to produce a corona discharge in said gap for ionizing the gas within the ar ticle to form a gaseous conductive backing element therein;

means for establishing electrostatic charges of opposite polarity on said printing element and on the interior surface of said hollow article through said gaseous conductive element to produce an electrostatic field between said element; and

means for feeding printing material to said printing element, whereby particles of said printing material are electrostatically charged by contact with said element and move across said electrostatic field onto said external area of the article.

7. In apparatus for printing on a gas-filled hollow ar- 5 ticle by electrostatic deposition of charged particles of printing material on the external surface of the article, the combination of:

a pair of electrodes spaced apart a predetermined distance and mounted in an insulating member, said electrodes being movable into and out of the gasfilled article;

a first source of potential connected to said electrodes to produce a corona discharge between said electrodes while they are within the article for ionizing the gas therein to produce a gaseous electroconductive element within the article and extending over the interior surface of the article opposite said exterior area to be printed upon;

means for establishing electrostatic charges of opposite polarity on said printing element and on said article,

through said gaseous element, to produce and maintain an electrostatic field between said elements;

and means for feeding said particles of printing material to said printing element, whereby said particles are charged by the printing element and propelled through said electrostatic field into printing contact with said external area of the article.

8. The apparatus set forth in claim 7 with the addition of an ionizer external to said article;

a second source of potential connected to said external ionizer; and

means for feeding ionized gas from said external ionizer to and through the interior of said article during said electrostatic printing operation.

9. The apparatus set forth in claim 7 wherein the electric potential at said first source is between 2000 and 15000 volts.

10. The apparatus of claim 8 wherein the potential at 0 said first source is between 2000 and 15000 volts; and the potential at said second source is about 5000 to 20000 volts.

References Cited UNITED STATES PATENTS 2,824,813 2/1958 Fauer et al. 2,931,688 4/1960 Innes et al. 2,957,077 10/ 1960 Hay. 3,017,339 1/1962 Dewey.

3,238,053 3/1966 Morgan.

3,296,963 1/1967 Rarey et al.

EUGENE R. CAPOZIQ, Primary Examiner.

ROBERT E. PULFREY, E. S. BURR, Examiners. 

6. IN AN APPARATUS FOR PRINTING BY ELECTROSTATIC DEPOSITION ON GAS-FILLED HOLLOW ARTICLES WHEREIN AN ELEMENT IS SPACED AT A SUBSTANTIALLY UNIFORM DISTANCE FROM AN EXTERNAL AREA OF A HOLLOW ARTICLE TO BE PRINTED UPON, AND THE THICKNESS OF SAID ARTICLE THROUGH SAID AREA IS SUBSTANTIALLY UNIFORM, THE COMBINATION COMPRISING: A SOURCE OF ELECTRIC POTENTIAL: A PAIR OF ELECTRODES MOUNTED IN AN INSULATING MEMBER AND EXTENDING THEREFROM IN PARALLELISM ONE RELATIVE TO THE OTHER LEAVING A PREDETERMINED GAP THEREBETWEEN, SAID ELECTRODES BEING INSERTABLE INTO THE GASFILLED INTERIOR OF SAID ARTICLE AND CONNECTED TO SAID SOURCE OF ELECTRIC POTENTIAL TO PRODUCE A CORONA DISCHARGE IN SAID GAP FOR IONIZING THE GAS WITHIN THE ARTICLE TO FORM A GASEOUS CONDUCTIVE BACKING ELEMENT THEREIN; 